title: Exploring alternative biomaterials for diagnosis of pulmonary tuberculosis in HIV-negative patients by use of the GeneXpert MTB/RIF assay.
abstract: The utility of the GeneXpert MTB/RIF (Xpert) assay for detection of Mycobacterium tuberculosis in sputum samples has been extensively studied. However, the performance of the Xpert assay as applied to other readily accessible body fluids such as exhaled breath condensate (EBC), saliva, urine, and blood has not been established. We used the Xpert assay to test EBC, saliva, urine, and blood samples from HIV-negative, smear- and culture-positive pulmonary tuberculosis (TB) patients for the presence of M. tuberculosis. To compare the ability of the assay to perform bacterial load measurements on sputum samples with versus without sample processing, the assay was also performed on paired direct and processed sputum samples from each patient. The Xpert assay detected M. tuberculosis in none of the 26 EBC samples (sensitivity, 0.0%; 95% confidence interval [95% CI], 0.0%, 12.9%), 10 of the 26 saliva samples (sensitivity, 38.5%; 95% CI, 22.4%, 57.5%), 1 of 26 urine samples (sensitivity, 3.8%; 95% CI, 0.7%, 18.9%), and 2 of 24 blood samples (sensitivity, 8.3%; 95% CI, 2.3%, 25.8%). For bacterial load measurements in the different types of sputum samples, the cycle thresholds of the two M. tuberculosis-positive sputum types were well correlated (Spearman correlation of 0.834). This study demonstrates that the Xpert assay should not be routinely used to detect M. tuberculosis in EBC, saliva, urine, or blood samples from HIV-negative patients suspected of having pulmonary tuberculosis. As a test of bacterial load, the assay produced similar results when used to test direct versus processed sputum samples. Sputum remains the optimal sample type for diagnosing pulmonary tuberculosis in HIV-negative patients with the Xpert assay.
authors.affiliation: Center for Infectious Diseases, New Jersey Medical School, Rutgers Biomedical & Health Sciences (formerly UMDNJ), Newark, New Jersey, USA.
authors.forename: Shubhada
authors.initials: S
authors.lastname: Shenai
authors.forename: Danielle
authors.initials: D
authors.lastname: Amisano
authors.forename: Katharina
authors.initials: K
authors.lastname: Ronacher
authors.forename: Magdalena
authors.initials: M
authors.lastname: Kriel
authors.forename: Padmapriya P
authors.initials: PP
authors.lastname: Banada
authors.forename: Taeksun
authors.initials: T
authors.lastname: Song
authors.forename: Myungsun
authors.initials: M
authors.lastname: Lee
authors.forename: Joon Sung
authors.initials: JS
authors.lastname: Joh
authors.forename: Jill
authors.initials: J
authors.lastname: Winter
authors.forename: Rich
authors.initials: R
authors.lastname: Thayer
authors.forename: Laura E
authors.initials: LE
authors.lastname: Via
authors.forename: Soyeon
authors.initials: S
authors.lastname: Kim
authors.forename: Clifton E
authors.initials: CE
authors.lastname: Barry
authors.forename: Gerhard
authors.initials: G
authors.lastname: Walzl
authors.forename: David
authors.initials: D
authors.lastname: Alland
mesh_terms: D000328:Adult; D001431:Bacteriological Techniques / Q000379:methods*; D001826:Body Fluids / Q000382:microbiology*; D006801:Humans; D025202:Molecular Diagnostic Techniques / Q000379:methods*; D009169:Mycobacterium tuberculosis / Q000235:genetics / Q000302:isolation & purification*; D012680:Sensitivity and Specificity; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis* / Q000382:microbiology*